Severe weather expected to affect the D.C. area again today

by Alex Liggitt

Take a look at{ }some of the rainfall totals from this morning across the D.C. area. Many locations received three-quarters to an inch of rainfall which puts a good bite into the deficit which is now up to 7 and 8 inches below normal for the year at the major D.C. airports.

Skies are now beginning to clear some across the region, which will be very important to what will occur later this afternoon and evening.

Visible satellite image from 11:15am

Above is the satellite image from 11:15 a.m. today, still showing an abundance of cloud cover but some clearing west of the city, mainly around the Blue Ridge Mountains and Shenandoah Valley. As the cold front is still located over the Ohio Valley as of noon, this will allow for more sunshine and lead to warmer temperatures and thus greater levels of instability later today.

Here's what is working for the D.C. area to get severe weather. Plenty of moisture is available, and precipitable water values are around 2 inches, which means any storm this afternoon will have the capability to bring very heavy rainfall in a short period of time. Instability will also be on the rise as skies clear this afternoon and temperatures warm into the upper 80s.

Along with the instability, the shear in the atmosphere will be on the rise as the area of low pressure moves closer to the region to the northwest. Finally, the necessary lifting mechanism will be in place, as the cold front pushes into our area later this afternoon and evening. All of these ingredients are needed for storms.

Slight Risk area issued by the Storm Prediction Center

There are some factors that may limit the severe potential, such as{ }if{ }the skies don't{ }completely clear. This will limit the heating and instability. Also, the shear doesn't appear to be that strong, though still strong enough for damaging winds.

Finally, the timing as right around sunset when storms typically begin to diminish in intensity. Unfortunately, I wouldn't rely on that either as we saw that scenario last night in Montgomery County where 10,000 people lost power once again.

So what are my actual thoughts on what we can see and when? As of Noon, storms are beginning to fire across central and eastern Ohio. It is this line of storms developing that I think will be our main focus later this evening into tonight.

High Resolution Rapid Refresh Model showing a line of storms around 7pm

Checking not only the current conditions but also many models, my thought is we'll see storms over the mountains around 4 p.m. and closer to the D.C. area around 7 p.m. or 8 p.m. this evening.

I think they will either be in the form of a line or clusters along a line and have the potential for very heavy rainfall, a lot of lightning and damaging winds.

I have also talked to Meteorologist Adam Caskey, and we both agree the potential for a tornado cannot be ruled out, but we think if there is one it would be weak and short-lived. The shear profiles just don't make us think there is a large potential for tornadoes. The whole team will continue to keep an eye on this developing situation and will keep you updated through the rest of the day.